Mechanics Parameters’ Measurement Of Soft Tissue In Vitro And Its Application In Virtual Surgery System.

The progress of Virtual Reality Technology,make it possible to establish a Virtual Surgery System. With the help of haptic device, the doctors could perform operations in virtual environment. Also, they could acquire the real force, touch and visual feedback. In the process of establishing the physical model of the virtual surgery system, the soft tissue’s mechanical property parameter have become the constraint of virtual organ physical model’s property. The measurement of soft tissue organ’s real mechanical performance parameters has a great significance to improve the force feedback of virtual surgery system.Based on the study of measuring of soft tissue mechanical parameters at home and abroad, the research topic will establish a new type of soft tissue mechanical parameters’measuring platform, measure the mechanical parameters of livers and apply the result in the Virtual surgery system. After that, the manipulator will acquire the force feedback effects that close to the real. The main research contents are as follows:Researching the virtual surgery system’s kernel module. Establishing the Virtual livers and surgical instruments’ geometric model and improving the speed of collision detection through the bounding box method. Analyzing the soft tissue’s mechanical property. Using the three parameter model to describe soft tissue’s viscoelasticity,confirm the livers’ elastic coefficient, viscosity coefficient and the outer organization damage threshold Fm. They are the core mechanical parameters of establishing the livers’ physical model.Establishing a brand new soft tissue parameters’ measuring platform. extending the function of Phantom Omni Robot. Using the Phantom Omni Robot in the measurement of soft tissue’s deformation. Designing the Spherical algorithm and using the Matlab to matching the"club length L" of measuring platform. Using the "D-H" algorithm to establish the Forward kinematics modeling and then get the coordinates of the end point. Compiling the "M" file to analyze the work space of the end point. Designing the clamping mechanism and the support organization to assist the operation in experiment. Designing an algorithm to calculate the weight compensation of the end of the force sensor and the threshold of contact force.With the help of the programming software, we can measure the livers’ deformation and the contact force.Designing the uniaxial compression experiment and presenting a method of segmentation to fit the elastic coefficient, fitting the livers’ elastic coefficients in different deformation stages. Designing the stress relaxation experiment to fit the livers’ viscosity coefficient. Designing the puncture experiment, analyzing the maximum of the livers’ outer organization when it is punctured, that is the destructive threshold (Fm) of livers’ outer organization.Taking use of the mechanical parameters of liver in the Virtual Surgery System. Doctors could stretch or compress the liver in the virtual environment, then fell the Force feedback by the Phantom Omni. Designing a compression experiment,compressing a whole liver,measuring the relationship between the deformation force and deformation. Comparing this relationship and the relationship of deformation force and deformation in the virtual environment to verify the correctness of virtual surgery system. It is proving that the mechanical properties of the real liver could improve the haptic experience of the Virtual surgery system. Establishing a Virtual surgery system based on the mechanical parameters of a real liver, providing a more complete haptic and visual experience for the doctors.